Method and apparatus for detection of concealed objects in passive thermal images using environment control

• US 8,835,849 B1
• Filed: 02/10/2011
• Issued: 09/16/2014
• Est. Priority Date: 02/10/2010
• Status: Expired due to Fees

• Current Assignee: MVT Equity LLC
• Original Assignee: MVT Equity LLC
• Inventors: Williams, Thomas D.
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Jo, Taeho
• Application Number:
  US13/024,853
• Time in Patent Office: 1,314 Days
• Field of Search: 348/162, 250/336.1
• US Class Current: 250/336.1
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging

Abstract

A method for obtaining a reflectance image from a plurality of thermal images utilizes a technique of A) obtaining a first thermal image of a subject, the first image containing both temperature and reflectance data; B) changing the environmental temperature of the scene, C) obtaining a second thermal image of the subject, the second image containing both temperature and reflectance data from the scene with said changed environmental temperature; and D) deriving a third image from the first and second images, that third image being essentially a reflectance image. In one embodiment, the third image is derived by subtracting the data in the first image from the data in the second image, or subtracting the data in the second image from the data in the first image. In another embodiment, either of the first or second images are processed along with the third image to produce a temperature image substantially devoid of reflectance information. A system for performing such techniques is also disclosed.

Claims

1. A method for obtaining a reflectance image of a concealed object at a scene from a plurality of thermal images, the method comprising:

obtaining a plurality of images, the plurality of images containing both temperature and reflectance data;

synchronously changing illumination conditions at the scene between at least two different states for pairs of first and second images of the plurality of images;

and

deriving a third image from a pair of the images, the third image being a reflectance image,

wherein a concealed object, with one of lesser or greater reflectance than reflectance generated by a human surface, generates a visible contrast on the third image.

2. The method of claim 1 wherein the third image is derived by subtracting data in a first image of the pair from data in a second image of the pair.

3. The method of claim 1 wherein the third image is derived by subtracting data in a second image of the pair from data in a first image of the pair.

4. The method of claim 1 wherein the third image is pointwise multiplied by a respective environmental temperature at the scene, then pointwise subtracted from one of the first and second images of the pair, and then pointwise divided by the third image everywhere subtracted from the value 1 to produce a temperature image devoid of reflectance information.

5. A method for obtaining a thermal reflectance image, the method comprising:

obtaining a plurality of thermal images of a human subject at a scene, the plurality of thermal images representing a mixture of temperature data and reflectance data, the first plurality of thermal images obtained at a first environmental temperature;

changing the first environmental temperature of the scene to a second environmental temperature;

obtaining a second plurality of thermal images of the human subject at the scene at the second environmental temperature, the second plurality of thermal images representing a mixture of temperature data and reflectance data;

creating a third image from data of the first and second plurality of thermal images, the third image being a composite reflectance image substantially devoid of temperature data from the first and second plurality of thermal images;

deriving an additional temperature image from the first and second plurality of thermal images and the composite reflectance image by;

composing a first composite image from the first plurality of images obtained at the first environmental temperature,

composing a second composite image from the second plurality of images obtained at the second environmental temperature,

composing a third composite image from the first and second composite images by pointwise subtracting one of the first and second composite image from the other of the first and second composite image, and

composing a fourth composite image by;

pointwise multiplying a known respective environmental temperature by the third image to obtain a first result,

pointwise subtracting the first result from one of the first and second image to obtain a second result, and

pointwise dividing the second result by the third image everywhere subtracted from a value of 1, resulting in a temperature image substantially devoid of reflectance information.

6. The method of claim 5 wherein creating the third image comprises:

subtracting one of the first and second plurality of thermal images from the other of the first and second plurality of thermal images.

7. A method for obtaining a thermal reflectance image, the method comprising:

obtaining a plurality of thermal images of a human subject at a scene, the plurality of thermal images representing a mixture of temperature data and reflectance data, the first plurality of thermal images obtained at a first environmental temperature;

changing the first environmental temperature of the scene to a second environmental temperature;

obtaining a second plurality of thermal images of the human subject at the scene at the second environmental temperature, the second plurality of thermal images representing a mixture of temperature data and reflectance data;

creating a third image from data of the first and second plurality of thermal images, the third image being a composite reflectance image substantially devoid of temperature data from the first and second plurality of thermal images;

pointwise subtracting pairs of thermal images resulting in a third plurality of images representing reflectance data, wherein each pair of thermal images comprises a thermal image from the first plurality of thermal images and a thermal image from the second plurality of thermal images; and

combining the third plurality of images into a single reflectance image.

8. A method for obtaining a thermal reflectance image, the method comprising;

obtaining plurality of thermal images of a human subject at a scene, the plurality of thermal imagines representing a mixture of temperature data and reflectance data, the first plurality of thermal images obtained at a first environmental temperature;

changing the first environmental temperature of the scene to a second environmental temperature;

obtaining a second plurality of thermal images of the human subject at the scene at the second environmental temperature, the second plurality of thermal images representing a mixture of temperature data and reflectance data;

creating a third image from data of the first and second plurality of thermal images, the third image being a composite reflectance image substantially devoid of temperature data from the first and second plurality of thermal images;

creating a fourth plurality of temperature images substantially devoid of reflectance information by;

pointwise multiplying a known respective environmental temperature by the third plurality of the reflectance images to obtain a plurality of first results, pointwise subtracting one of the plurality of first results from the one of the first plurality of images or one of the second plurality of images image to obtain a plurality of second results, and pointwise dividing one of the plurality of second results by one of the third of plurality of the reflectance images everywhere subtracted from a value of 1, resulting in the fourth plurality of the temperature images substantially devoid of reflectance information, and combining the fourth plurality of temperature images into a single temperature image.

9. A system for imaging a subject at a scene, the system comprising:

an imaging device for capturing a plurality of thermal images of the subject, the thermal images containing both temperature and reflectance data;

a device for synchronously changing illumination conditions at the scene between at least two different states, the device providing an illumination in each state sufficiently large and uniform to change an effective temperature impinging on the subject at wavelengths at which the imaging device operates, so that a thermal image of the subject exists for each of the two different states;

a memory coupled to the imaging device for storing the plurality of thermal images of the subject; and

a processor coupled to the memory for creating composite processed images from data of a plurality of the thermal images, the composite processed images substantially devoid of temperature data from the plurality of thermal images of the subject.

10. A method for obtaining a reflectance image from a plurality of a passive millimeter sensor images, the method comprising:

obtaining a first plurality of passive millimeter images of a subject within a control environment, the first plurality of passive millimeter images containing both temperature and reflectance data;

changing the environmental temperature of the scene uniformly,

obtaining a second plurality of passive millimeter images of the subject, the second plurality of passive millimeter images containing both temperature and reflectance data from the scene including the subject; and

deriving a third image from the first and second plurality of passive millimeter images, the third image being a reflectance image, wherein a concealed object, with one of lesser or greater reflectance than reflectance generated by a human, generates a visible contrast on the third image.

11. A system for imaging a subject at a scene, the system comprising:

a passive millimeter imaging device for capturing a plurality of images of the subject within a control environment, the plurality of passive millimeter images containing both temperature and reflectance data;

a temperature control device for changing illumination conditions at the scene between at least two different temperature states, the temperature control device providing an illumination in each temperature state sufficiently large and uniform to change an effective temperature impinging on the subject at which the passive millimeter imaging device operates so that the imaging device can capture a plurality of images of the subject at two separate temperature states;

a memory coupled to the imaging device for storing the plurality of images of the subject; and

a processor coupled to the memory for creating composite processed images from data of the plurality of the images, the composite processed images substantially devoid of temperature data from the plurality of images of the subject and the composite processed images being reflectance images.

12. The system of claim 11 wherein the processor further creates an image essentially devoid of reflectance data.

13. The system of claim 12 wherein the processor further determines the existence of a threat object based on one of the plurality of images, the image devoid of temperature data, the image devoid of reflectance data, or any combination thereof.

14. The system of claim 11 wherein only one composite image is created for the subject.

15. The system of claim 11 wherein a plurality of composite images are created for the subject.

16. The system of claim 11 wherein a continuous plurality of composite images is created for the subject.